Diode Laser Development & Manufacturing: FAQ

What is a diode laser?

A diode laser (Light Amplification by Stimulated Emission of Radiation) utilizes a semiconductor material (e.g. GaAlAs, InGaAs) as the active medium to generate light. Light is emitted out of the active region of the semiconductor, and can be tailored to a desired geometry during the processing of the semiconductor wafer for different applications. Individual diode lasers can be produced with a single emitter device or in a bar with many emitters. Bars can then be stacked into arrays to increase the overall output power. The electro-optical efficiency of a diode laser is about 50% making it the most efficient of all lasers. As well as being efficient, diode lasers are highly reliable and require very limited space, making them compact and portable.

The laser light emitted from a diode laser array is passed through a series of optical components and then focused into a fiber. The light that exits the fiber’s end has a circular, uniform beam profile. This symmetric beam simplifies the end user’s application by eliminating complex optics. Fibers can be manufactured in a variety of lengths giving the end user the flexibility of having the laser and work piece at separate locations.

What is the difference between a laser module and a turnkey system?

A laser module is a stand alone laser that will include the semiconductor laser array, beam shaping optics and, if applicable, a fiber or window. The turnkey diode laser system consists of the laser module and all peripheral components (e.g. driver, cooling, controller, user interface and safety circuits), which allow you to operate the laser in one enclosure.

What information do I need to specify a laser for my application?

To determine what laser will work best for your application, it is necessary to understand your process requirements (welding, brazing, cladding, ablation, etc.) and materials requirements (stainless, copper, iron, plastic, etc.) Visotek can assist you in determining the correct laser output power, wavelength, fiber core diameter or spot size.

What is the Numerical Aperture (NA) of a fiber?

The numerical aperature is an indicator of the maximum acceptance angle an optical fiber accepts and propogates the laser light. It determines the size of the processing optic lenses and spot size (see BPP below). The NA is a measure of the maximum angle of the cone the laser beam exiting the optical fiber.

The NA of a fiber is defined as the Sine of the maximum divergence half-angle the laser radiation is emitted from the fiber tip in air.

NA = n· sin (in air: n=1)

What is the Beam Parameter Product (BPP)?

The BPP quantifies the quality of a laser beam, and how well it can be focused to a small spot. This important parameter determines the spot size of a processing optic head. The beam parameter product (BPP) is defined as the product of the tangent of a laser beam's divergence half-angle and the radius of the beam at its narrowest point (the beam waist ) The most common unit used for the BPP is mm · mrad:

BPP =· tan= constantBPP =· (for small angles)

What is a step-index fiber?

A step-index fiber is comprised of three basic elements: the core, the cladding and the coating/buffer. The core is a glass optical fiber with a uniform refractive index. The cladding is placed outside the core and has a sharply lower refractive index than the core. When the laser light is introduced into the fiber’s core, the light travels through the fiber, reflecting off the cladding forcing the light back into the core of the fiber guiding the laser light over long distances with minimal losses. The coating/buffer is placed onto the cladding to protect against mechanical damage and to increase strength for the brittle fiber.

What is a laser processing head?

A laser processing head is a series of optical components attached to the output end of a fiber. The processing head directs the laser beam to the work piece in a controlled manner. Processing heads can be designed to either focus the laser energy narrowly to achieve a given spot size or collimate a broader optical beam, depending on the desired application.

Is the laser beam harmful to my eyes and skin?

Potentially yes. Visotek makes Class 4 lasers and they can burn the skin, in addition to potentially devastating and permanent eye damage as a result of direct or diffuse beam viewing. These lasers may ignite combustible materials, and thus may represent a fire risk. Class 4 lasers must be equipped with a key switch and a safety interlock.

Caution should always be used when operating any laser. Proper personal protection should be available and used when a laser is in operation.

Visit the Laser Institute of America (http://www.laserinstitute.org/) for further information and training for your laser safety officer and personnel that will be operating laser equipment.

Does Visotek sell spare parts for lasers?

Naturally we supply Spare parts for Visotek Lasers, and we can also supply Spare parts for Lasers manufactured by other companies. With a vast network of laser suppliers, Visotek can acquire the spare parts your system requires in a timely and cost efficient manner, making us a premier supplier of laser components, fibers and optics.